With the development of integrated circuits technology, device feature size is becoming smaller and low electron and hole mobility in bulk silicon (Si) material has become the bottleneck of enhancing device performance. Strained silicon is formed by epitaxially growing silicon on materials that have different lattice constant from silicon, or by stretch or compressive deformation of silicon lattice structure through other processes. Because strained silicon can effectively improve carrier mobility, it has become a candidate substrate material for semiconductor technology node of the next generation. Since SiGe substrate has different lattice constant from Si, there would be lattice mismatch between SiGe substrate and epitaxial Si grown thereon and such lattice mismatch will therefore induce strain in epitaxial Si layer. Due to lattice structure distortion, strained silicon material can simultaneously enhance electron and hole mobility, and strained silicon on insulator (sSOI) features strong points of both silicon on insulator (SOI) and strained silicon, enjoying extensive application prospect in integrated circuits technology.
Strained silicon on insulator can also be a combination of strained Si and (strained) SiGe, that is to say, a dual channel layer structure formed by strained Si/ (strained) SiGe (where Si is the surface layer and SiGe is the buried layer). In unique energy band structure of dual channel, electrons are restricted within strained Si layer and can get high electron mobility, while holes are restricted within (strained) SiGe layer and can get high hole mobility.
Therefore, the present invention provides a process of fabricating strained Si/SiGe dual channel material based on SOI substrate, which can be used to simultaneously provide high-mobility channel material for NMOS and PMOS.